1. Field of the Invention
The present invention relates to an image processing system such as a print system for use in a copying machine, a printer and the like, and also relates to an image processing method.
2. Description of Related Art
In a print system as one of image processing systems, image data sent from an image scanner, a personal computer and other equipments is written into a memory such as a DRAM (Dynamic Random Access Memory) after being stored in a hard disk or without being stored in a hard disk. The written-image data is read out from the memory, and then is subjected to an image processing to be printed.
Generally, image data of a plurality of pages is written into a DRAM in a compressed state at a compression rate of from 100% to 5% depending on the original attributes. For example, the compression rate of an image data of a page including many characters, is excellent. On the other hand, the compression rate of an image data of a page including a great amount of half tones such as a picture, is poor.
Furthermore, as an image processing mode, an electronic sort mode and a memory recall mode are known. In the electronic sort mode, a processing of reading out an image data from a DRAM in a predetermined page order, for example, page 1 to page N →page 1 to page N → . . . , and printing the image, is repeated several times. In the memory recall mode, image data of an image once printed is held in a memory such as a DRAM or a hard disk. Thereafter, the image data is read out from the memory again based on, for example, a re-print request of a user, and printed.
As one example of a prior art of an image processing system disclosing a part of the aforementioned structure, Japanese Unexamined Laid-open Patent Publication No. H10-304111 is known. In this prior art, in cases where empty capacity of a DRAM becomes insufficient during a writing of image data into the DRAM or it becomes impossible to secure a predetermined empty capacity, empty capacity of the memory is secured by deleting image data from the page to be printed first among image data of pages 1 to N to be stored in the DRAM from the memory in sequence, i.e., by deleting image data from page 1 from the memory in sequence. Then, in the empty area of the memory, image data of the subsequent page is written to continue the printing operation.
However, in the aforementioned conventional image processing system, in cases where empty capacity of a memory becomes insufficient or it becomes impossible to secure a predetermined empty capacity during the writing of image data when it is repeatedly performed to read and then print one set of image data of page 1 to page N in the page order as in the aforementioned electronic sort mode or memory recall mode, the image data of page 1, which is the first page to be subjected to an image processing, is deleted first. Accordingly, it is required to newly obtain the image data of page 1 when the image data is to be printed again.
For example, in cases where a printer is connected by a hard disk in which image data of page 1 is stored, it is required to store the image data into a DRAM after reading out the image data from the hard disk. Furthermore, in cases where a printer is not connected by a hard disk or a printer is connected by a hard disk in which the image data of page 1 is not stored, it is required to store the image data into a DRAM by reading it from the original image by, for example, an image scanner, or request a re-transmission of the image data to a personal computer.
A processing time required for a reading of image data from a hard disk, a re-reading of an original image by an image scanner or a re-transmission of image data from a personal computer is longer than a processing time required for a reading of image data from a DRAM. Accordingly, in the event that a document of pages 1 to N is printed so as to obtain plural sets of documents, it requires a longer time to print the first page of the document to be printed second and that of the subsequent documents (i.e., the first page to be printed in each document) than that of the document to be printed first.
In other words, in a conventional print system, there is a drawback that the image processing speed as a whole becomes slower when memory capacity becomes insufficient.
Such a drawback does not always occur only in a print system but may occur in other image processing systems.